﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Diagnostics;

using Microsoft.Practices.Unity;

namespace EzDesk.MVVMBase
{
    public interface IViewModel
    {}

    public abstract class ViewModelBase :IViewModel, INotifyPropertyChanged, IDisposable
    {
        #region Debugging Aides

        /// <summary>
        /// Warns the developer if this object does not have
        /// a public property with the specified name. This 
        /// method does not exist in a Release build.
        /// </summary>
        [Conditional("DEBUG")]
        [DebuggerStepThrough]
        public void VerifyPropertyName(string propertyName)
        {
            // Verify that the property name matches a real,  
            // public, instance property on this object.
            if (TypeDescriptor.GetProperties(this)[propertyName] == null)
            {
                string msg = "Invalid property name: " + propertyName;

                if (this.ThrowOnInvalidPropertyName)
                    throw new Exception(msg);
                else
                    Debug.Fail(msg);
            }
        }

        /// <summary>
        /// Returns whether an exception is thrown, or if a Debug.Fail() is used
        /// when an invalid property name is passed to the VerifyPropertyName method.
        /// The default value is false, but subclasses used by unit tests might 
        /// override this property's getter to return true.
        /// </summary>
        protected virtual bool ThrowOnInvalidPropertyName { get; private set; }

        #endregion // Debugging Aides

        #region INotifyPropertyChanged Members

        /// <summary>
        /// Raised when a property on this object has a new value.
        /// </summary>
        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        /// Raises this object's PropertyChanged event.
        /// </summary>
        /// <param name="propertyName">The property that has a new value.</param>
        protected virtual void RaisePropertyChanged(string propertyName)
        {
            this.VerifyPropertyName(propertyName);

            PropertyChangedEventHandler handler = this.PropertyChanged;
            if (handler != null)
            {
                var e = new PropertyChangedEventArgs(propertyName);
                handler(this, e);
            }
        }

        #endregion // INotifyPropertyChanged Members


        #region IDisposable Members

        /// <summary>
        /// Invoked when this object is being removed from the application
        /// and will be subject to garbage collection.
        /// </summary>
        public void Dispose()
        {
            this.OnDispose();
        }

        /// <summary>
        /// Child classes can override this method to perform 
        /// clean-up logic, such as removing event handlers.
        /// </summary>
        protected virtual void OnDispose()
        {
        }

        #endregion // IDisposable Members
    }


    /// <summary>
    /// Base class for all ViewModel classes in the application.
    /// It provides support for property change notifications 
    /// and has a DisplayName property.  This class is abstract.
    /// </summary>
    public abstract class ViewModelBase<TViewContract> : ViewModelBase where TViewContract : IView
    {

        #region Constructor

        protected ViewModelBase()
        {
        }



        protected ViewModelBase(TViewContract view)
        {
            this._view = view;
            this._view.ViewModel = this;
        }

        protected ViewModelBase(IUnityContainer container)
        {
            this.Container = container;
        }

        #endregion // Constructor

        protected virtual IUnityContainer Container { get; set; }

        #region View

        private TViewContract _view;

        public virtual TViewContract View
        {
            get
            {
                if (_view == null)
                {
                    this._view = Container.Resolve<TViewContract>();
                    this._view.ViewModel = this;
                }
                return _view;
            }
            set
            {
                this._view = value;
                if(this._view != null)
                    this._view.ViewModel = this;
            }
        }

        #endregion // View

        #region DisplayName

        /// <summary>
        /// Returns the user-friendly name of this object.
        /// Child classes can set this property to a new value,
        /// or override it to determine the value on-demand.
        /// </summary>
        public virtual string DisplayName { get; protected set; }

        #endregion // DisplayName

        protected override void OnDispose()
        {
            if(_view != null)
                View.ViewModel = null;
            this._view = default(TViewContract);
            base.OnDispose();
        }

#if DEBUG
        /// <summary>
        /// Useful for ensuring that ViewModel objects are properly garbage collected.
        /// </summary>
        ~ViewModelBase()
        {
            string msg = string.Format("{0} ({1}) ({2}) Finalized", this.GetType().Name, this.DisplayName, this.GetHashCode());
            System.Diagnostics.Debug.WriteLine(msg);
        }
#endif

    }
}
